1. Field of the Invention
The present invention relates to a key switch device having a key top which is guided up and down with a pair of link members to perform a switching action, a keyboard including the key switch device, and an electronic apparatus provided with the keyboard.
More particularly, the present invention relates to a key switch device which does not need a rubber spring generally used in a conventional key switch device and a complicated key top urging mechanism, and which can realize a key operation with a fine click touch in operating a key top and freely design the click touch, so that the cost of the whole key switch device can be reduced, and a keyboard provided with the key switch device and an electronic apparatus provided with the keyboard.
2. Description of Related Art
In association with the reduction in size, thickness, and others of a notebook-size personal computer which is one of electronic instruments, conventionally, there have been proposed various types of key switch devices used for a keyboard provided in the notebook-size personal computer. Such the key switch devices generally use a rubber spring for urging a key top upward and hold it in a non-pressed position (an xe2x80x9cupxe2x80x9d position), while buckles with a click when the key top is pressed down, then performing a switching operation, and returns the key top to the up position after the switching operation.
The rubber spring is usually made of one of silicon rubber, EPDM rubber, etc., which is in general high in cost and complex in properly assembling in place in the key switch device. The switching characteristics of the key switch device largely depend on the property of the rubber spring. The use of the rubber spring would therefore inhibit the flexible or free change of the switching characteristics of the key switch device.
In view of the circumstances, many proposals to realize a key switch device without use of a rubber spring have been presented in recent years. For instance, Japanese unexamined application laid-open No. 10-172380 discloses a key switch device in which a pair of a first and second links are movably arranged between a hook of a key top and a hook of a base mold to guide the key top in a vertical direction, and a rubber sheet stretched over between joint portions of the links. In such the key switch device, a circular projection formed on the back surface of the key top is made into close contact with the rubber sheet while the key top is not pressed, thus holding the key top in a non-pressed position. Upon pressure of the key top, the key top presses the rubber sheet downward through the circular projection as increasing a tension of the rubber sheet so that the rubber sheet projects downward through a through hole, thereby performing a switching operation, with a click, a switching area of a membrane sheet supported on a bottom plate.
It is to be noted that, on release of the pressure of the key top, the key top is moved upward by an elastic force of the rubber sheet to the original non-pressed position.
The above key switch device disclosed in Japanese unexamined application laid-open No. 10-172380, using no rubber spring, could achieve the increase in flexibility of key switch design without influence of the size of a rubber spring.
Although the above key switch device is not provided with a generally used rubber spring, however, the rubber sheet simply substitutes for the rubber spring. In view of the structure of the key switch device needing such the rubber sheet, the key switch device is still insufficient in reduction of cost of the whole key switch device. The work of stretching the rubber sheet over between the joints of the pair of links also would complicate the work of assembling the key switch device.
Although the above key switch device could perform a switching operation with a click touch when the key top is pressed down, it is difficult to provide a flexibly designed click touch.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a key switch device capable of performing a key operation with a fine click touch in operating a key top and also capable of providing a flexibly designed click touch, without needing a rubber spring and a complicated key top urging mechanism, thereby reducing the cost of the whole key switch device, and a keyboard provided with the key switch device and an electronic apparatus provided with the keyboard.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a key switch device including a key top and a pair of first and second link members movably arranged under the key top, the first and second link members being used for guiding the key top in a vertical direction to perform a switching operation on a switching section, the device further including a first cam portion formed in the first link member, a second cam portion formed in the second link member, and an elastic portion formed in each of the first and second cam portions, for urging the first and second cam portions in a direction to come into contact with each other.
In the above key switch device, the first link member is provided with the first cam portion, the second link member is provided with the second cam portion, and the first and second cam portions are provided with the elastic portions for urging the first and second cam portions respectively in a direction of contacting with each other. By the contact state of the first cam portion of the first link member and the second cam portion of the second link member, and, the cooperation of the elastic portions of the first and second cam portions, the key top can be urged upward and held in the non-pressed position or be returned to the non-pressed position upon release of pressure of the key top. The key switch device is constructed with no use of a rubber spring and a complicated urging mechanism, so that the reduction in cost can be achieved.
The first and second cam portions are always in contact with each other through the elastic portions. The contact position therebetween varies with the vertical movement of the key top. Accordingly, change of the shapes of the first and second cam portions as required enables a flexible design of a click which generates in the key operation.
According to another aspect of the present invention, there is provided a keyboard to be used for inputting letters, symbols, and others, the keyboard including a key switch device that includes; a key top; a pair of first and second link members movably arranged under the key top, the first and second link members being used for guiding the key top in a vertical direction to perform a switching operation on a switching section; a first cam portion formed in the first link member; a second cam portion formed in the second link member; and an elastic portion formed in each of the first and second cam portions, for urging the first and second cam portions in a direction to come into contact with each other.
According to another aspect of the present invention, there is provided an electronic apparatus including a keyboard used for inputting letters, symbols, and others, the keyboard being provided with a key switch device that includes a key top, a pair of first and second link members movably arranged under the key top, the first and second link members being used for guiding the key top in a vertical direction to perform a switching operation on a switching section, a first cam portion formed in the first link member; a second cam portion formed in the second link member, and an elastic portion formed in each of the first and second cam portions, for urging the first and second cam portions in a direction to come into contact with each other; display means for displaying the letters, symbols, and others; and control means for controlling the display means to display the letters, symbols, and others based on input data from the keyboard.